1. Field of the Invention
The present invention relates to a base member for use in a motor and a disk drive apparatus.
2. Description of the Related Art
Conventionally, a disk drive apparatus such as a hard disk drive apparatus or the like is equipped with a spindle motor for rotating a disk. The disk drive apparatus includes a disk, a housing, a stator, a FPC (Flexible Printed Circuit), and so forth. The housing includes a cover member, a base member, and so forth.
In recent years, the disk drive apparatus is required to become smaller in height and size. Particularly, in order to further reduce the height of a disk drive apparatus of a 2.5 inch 7 mm-thickness or a 2.5 inch 5 mm-thickness which are used in small-size disk drive apparatuses, it is necessary to reduce the thickness of a housing or a motor arranged within the housing. In general, the motor includes a hub, a coil, a stator core, a wiring substrate, a base member, etc. When assembling the motor, these components are arranged to axially overlap with one another. In order for the thickness of the motor to become small, these components need to be made thin. However, if an attempt is made to reduce the overall height of the motor by reducing the turn number of the coils or the lamination thickness of the stator core, the magnetic fluxes generated in the stator during the operation of the motor are reduced such that the torque constant is reduced. It is therefore impossible to obtain the torque required for rotating the disk attached to the hub.
In order to reduce the height of the motor, it is therefore necessary to reduce the thickness of the base member, among the components of the motor, which dominates a large portion of the axial dimension of the motor. However, if the base member is merely made thin, the rigidity of the base member is reduced to a great extent. As a result, if a shocking force is applied from the outside to the base member, it is likely that the base member is broken and that the disk arranged within the housing is damaged.
With a view to solve this problem, it is thinkable to employ a method in which a thickness is secured by depressing only the portion of a base member where a circuit board or an integrated circuit is arranged, accommodating the circuit board or the integrated circuit in the depressed portion, and keeping the remaining portions of the base member not depressed. However, if an attempt is made to reduce the thickness of the base member through the use of this method, the thickness of the base member becomes extremely small and the rigidity becomes reduced in the depressed portion. In addition, a difficulty in machining the base member arises and the base member may be pierced during a machining process. The present inventors have solved this problem by employing the following structure.